The best way to learn about preventive maintenance is to look at as many specific preventive maintenance examples as possible. That way, you can easily learn what it is, how it works, and why it delivers so many benefits.
Let's build out some working definitions, packing in plenty of examples along the way.
What is preventive maintenance?
Preventive maintenance is a simple idea about reliability put into direct, systematic action. The idea is that it's always better to solve a small issue before it becomes a big problem. It's why you periodically check the oil in your car; it's easier and cheaper to change the oil than it is to replace a seized engine.
That's the fundamental idea. And the way it's put into direct action depends on the industry, but generally, in industrial or commercial settings, preventive maintenance is proactive maintenance that focuses on combinations of:
- Parts replacement
Jumping back to our car example one more time, inspections can be checking the oil and tire pressure. Adjustments might be to the fan belt or idle setting. Cleaning covers cleaning the air filter while lubrication involves adding grease or silicone to the hood latch or door hinges. Swapping out old window wipers for a new set is parts replacement.
What's the difference between preventive maintenance, PM, and a PM?
That second "a PM" is not a typo. People sometimes use PM when they mean preventive maintenance. It's the same as when people use the shorter, easier FBI instead of Federal Bureau of Investigation. What's much more common is people talking about a PM or PMs, which are scheduled preventive maintenance work orders. Someone might talk about needing to close out a PM or having three PMs coming up in the next week.
To make things even a bit more confusing, PM can also mean project management, which is a completely different topic. So, if you're searching online for information on preventive maintenance, use the full phrase or "PM" plus other terms to narrow down the results. For example, "maintenance PM."
Now that we know what it is in the broad sense let's start breaking it down into more specific types. The two big ones are related to timing.
What is calendar-based preventive maintenance?
You can also call it periodic or time-based preventive maintenance. Here, you schedule the maintenance according to calendar dates. You might adjust the conveyor belt once a week, check a pressure seal once a month, and inspect the roof every year in late fall before the first snow.
Time-based PMs: advantages
The advantage here is that because you're scheduling everything so far in advance, you can have everything ready when the PM comes up. Take that last preventive maintenance example, inspecting the roof every year in late fall. With all that lead time, you can make sure you have the right technicians on shift for the PM. Not everyone is good at spotting problems with roofs, but you have time to move schedules around and put together the right team. You can also make sure you have all the right tools and materials on hand. Calculate lead times and order in the materials to arrive a few days before the PM, cutting shipping and carrying costs. Let's add one more advantage: scheduling the PM for the right shift and time of day. In this example, the access point to the roof is close to some of your larger assets, so it's easier and safer to schedule the PM for the third shift, when the line is moving more slowly or sitting idle.
Calendar-based PMs are perfect when there is a close and consistent connection between time and usage. A good preventive maintenance example is a delivery truck that always runs the same route the same number of times a week. Or the pumps and filters on an indoor swimming pool. Within any given amount of time, they're going to cycle a predictable number of times. In other cases, you can use different failure metrics to establish the best times for PMs. For example, you can set a PM to check the band saw every 25 days if you know it's failed every 30 days over the last three months. To learn more, check out MTTR, MTBF, MTTF: A Complete Guide to Failure Metrics.
Calendar-based PMs are also great for tasks that require a lot of coordination between maintenance and other departments. For example, Hippo has a customer that runs a zoo with a world-class polar bear exhibit. One of the PMs is cleaning out the pool, which is a big job requiring a team of maintenance technicians working closely with the polar bears' keepers who are responsible for everyone's safety.
For assets with a much weaker connection between time and usage, calendar-based PMs can make less sense, and eventually, you end up over or under maintaining your assets. You're doing the maintenance too early, when the asset doesn't yet need it, or too late, when the asset has already developed more serious problems. The solution is the next type of preventive maintenance, meter based.
What is meter-based preventive maintenance?
Unlike calendar-based PMs, here you need to monitor how much assets are being used to determine when they need maintenance. You're not looking for signs of problems. Instead, you predetermine an amount of usage between PMs, and then keep tracking until you reach it.
Meter-based PMs: advantages
The advantage is that your program is much more in tune with your assets. Work gets done when it's needed, neither too early nor too late. This takes care of the problems of over and under maintaining assets.
But it's not without some challenges. First, you need to determine what to track for each asset. For a vehicle, you might want to track mileage. For a pump, cycles. For the widget-making machine on your line, the number of widgets produced. These are good for tracking usage, but not perfect. For example, the miles on a car driven by a lead-foot 16-year-old are not the same as the miles on a car lovingly pampered by a retired grade school teacher. In the end, though, manufacturers often provide suggestions on how to track usage and when to perform maintenance tasks.
Another challenge is that because you've tied the PMs to usage, it's a bit harder to prepare for them. With time-based PMs, you know right down to the hour when they're going to happen. But with usage-based PMs, you lose some of the advantages you get from advance scheduling. It's harder to get the right people and materials to the asset at the right time.
How do I know which assets to include in a preventive maintenance program?
Short answer: if it's light bulbs, don't add them. They're the classic example of an asset that you should let run to failure. Why? They're cheap to buy and have. It costs next to nothing to carry them in inventory because they don't take up a lot of room and they never go stale. Also, they're never critical to your operation. If one goes out, you can quickly and easily replace it, but there's generally no rush. So, if it's light bulbs, or anything that shares a lot of qualities with light bulbs, don't add them to the program.
For everything else, focus on criticality. Basically, ask yourself this question about each asset: If this asset stops working, how bad is bad? The key is to make sure to think of all the different ways it can be bad, including issues related to:
- Maintenance costs
- Regulatory compliance
- Workplace safety
- Overall lost production
Once you know the types, you can start to consider degrees. For a fuller explanation of how to choose which assets to include, check out How to Pick the Right Preventive Maintenance Strategy and Find the Best Maintenance Management Strategy.
How do I get started with preventive maintenance?
If you don't have one yet, get a modern CMMS software. If you have one but it's not delivering the results you were promised, get a new one. A cloud-based CMMS with real-time data updates and anytime, anywhere mobile access is the backbone of an efficient preventive maintenance program. It makes every step of setting up, scheduling, and tracking your program easier.
A good CMMS is great at collecting and safeguarding data, which you can then leverage to determine PM tasks and frequencies. Use the calendar view to see all your time-based PMs, and tie in meter readings to track usage-based PMs. Built-in inventory tracking, which connects directly to both on-demand and scheduled work orders, delivers the right parts to the right place at the right time. And because you eliminate the need to rush deliveries, you also get those parts at the right price.